One of the major inconveniences and sources of expense in the operation of a shaft furnace is the need to replace the refractory lining of the furnace at intervals. By cooling the refractory lining it can be made to last longer, but the replacement of the cooling means increases the complexity and expense of the re-lining operation. One method of cooling shaft furnaces known as plate cooling has been known for many years and has generally found favour. This method involves the provision of water-cooled plates in the refractory lining of the furnaces, which plates extend transversely with respect to the working surface of the lining. These plates are usually built into the furnace walls as the furnaces lining is built up. This type of cooling is particularly suitable for the bosh zone of the furnace although it can be used in other zones. It is usual for about seven to nine cooling plates to be interconnected by intermediate water inlet and outlets so that a single main water inlet and a single main water outlet only need be provided for this series of plates. This type of cooling is very efficient whilst it is operative normally since the cooled face of the plate is close to the inner face of the lining of the furnace. However, when leakage occurs, and in mid to late campaigns this is frequent, then serious water ingress can occur.